Abstract: The Knotty problems facing the washery are heavy load of flotation system and coal slurry treatment system, and deterioration of wash water. Through technical transformation of the coal slurry treatment system, the density of wash water is much reduced due to reduction of volume of accumulated slime and secondary slime contained, making it possible to turn a two-stage washing process into a 3-stage one. Through the upgrading process, there has been seen an enhanced coal cleaning efficiency, increased amount of raw coal treated and improved economic result.